Technical Abstract:
Fine mapping of a QTL located on chromosome 10 (SSC10) was conducted in a four-breed, white composite population of swine selected for ovulation rate (OR). Animals were selected for 11 generations for increased OR and compared to unselected controls (CO). The selection line had an increase of 3.0 corpora lutea (CL) and an increase of 0.3 pigs in total litter size as compared to controls. DNA was collected from 262 CO and 258 OR gilts and boars at generations 12 and 13. Six microsatellite markers, including two utilized in validation of the QTL, that spanned from 69cM to 96cM were genotyped. Utilizing SAS/Genetics, the marker which had showed the most significant (P<0.001) divergence between OR and CO lines was SW1041 (69cM). Significant differences (P<0.001) of SW1041 alleles on CL were identified with a model including allele, line, year born, season born, and sire as a random effect. The most frequent SW1041 allele in the OR line was associated with the second largest CL mean. Two markers (SWR1829, SW951) had the most frequent OR allele associated with greatest CL mean. An additional two markers (MRC1MS, GAD2) had an increase in the frequency of the OR line allele, compared to CO, which was associated with greatest CL mean for the marker. These data indicate that the divergence in allele frequencies on SSC10 between the OR and CO lines is likely due to a CL QTL and they refine the region in which a CL QTL is located. The selection line will be useful to identify genetic markers and causative genes for use in the industry.